JPS61198304A - Arm control system - Google Patents

Abstract

PURPOSE:To select automatically the attitude of an arm by using a ratio of the distance between a target position designated as a point on the operation course of the arm and the axis of the arm to that between the first and the second positions to interpolate the attitude. CONSTITUTION:The position and the attitude of an arm body 6 at a point nearest to an axis Z of the arm 6 are taught and stored preliminarily, and those at a point most distant from the axis Z are taught and stored preliminarily. A target position P is designated, and a distance R between the position P and the axis Z is obtained. The distance R is compared with a distance R1 between a position P1 and the axis Z and a distance R2 between a position P2 and the axis Z, and the target position and the target attitude are obtained to move the arm if R1<=R<=R2 is true. Thus, even when the arm is moved in a wide range, the attitude is automatically selected so as to utilize the moving range of the arm 6.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an arm 1tTIJ cape method for controlling the motion path of a multi-jointed arm that requires specifying a target position and a target posture.

(Prior art and its problems) In order to instruct the motion path of a multi-joint arm, it is necessary to specify a target and a target posture, and conventionally, the target position and posture have been specified in advance.

In addition, it is registered in the control device, and the registered target position and posture are sequentially read out at the time of actual work.
A method is used in which the arm is moved in accordance with this. Generally, a large number of target positions and postures are required to be registered in order to perform a series of tasks using an arm, and teaching for this registration requires a great deal of effort. Several teaching devices have been proposed to reduce the effort required for this teaching. In the conventional arm control method, a three-dimensional joystick is used to specify the direction and speed of movement of the arm, move it to a desired position, and register the position and posture at the point where it stops.
No. 190), the posture remained constant during the movement. In addition, when changing the posture, the three-dimensional joystick can be used by operating the changeover switch.
, Tear.

The robot moves to a desired posture by specifying the moving direction and speed of the posture, but the position remains constant during the movement.

If the position of a multi-joint arm is moved while maintaining a fixed posture, the range of movement will be greatly restricted due to restrictions on the rotation range of the joints that make up the arm.

Therefore, when moving over a wide range, it is necessary to select all postures depending on the position. Father, some tasks using multi-jointed arms require specifying the position, but posture is often not an issue. For example, when grabbing cylindrical objects placed randomly on a workbench and moving them without arranging them in a designated box, or using image information obtained from a hand camera attached to the end of the arm. This is the case when all moving objects are tracked using i. If such work is performed using the conventional arm control method, in order to move the arm over a wide range, it is necessary to repeatedly move the position and posture, and the changeover switch must be operated frequently. There were some gaps in operability. In addition, when considering the automatic execution of the above-mentioned work and moving the arm according to the position information of the target object obtained from a fixed camera or hand camera, the posture needs to be determined according to some standard. When postures are used, the movable range is greatly restricted for the reasons mentioned above, while with conventional control methods, it is extremely difficult to select a posture that effectively utilizes the arm movement range. .

(Object of the Invention) An object of the present invention is to provide an arm control method for controlling the motion path of a multi-joint arm that requires designation of a target position and a target posture, in which the target position is only specified when specifying the motion path. Now, we have developed an arm control method that eliminates the above-mentioned drawbacks of the conventional method, which makes it possible to automatically select the arm posture by effectively utilizing the arm movement range even when moving over a wide range. The purpose is to provide a method that can be implemented with a simple circuit configuration.

(Structure of the Invention) According to the present invention, there is provided a first position which is the position of the arm closest to the central axis of the arm, a first posture which is the posture of the arm in this first position, and a first posture of the arm in the first position; means for storing a second position that is the position of the arm farthest from the central axis and a second posture that is the posture of the arm at this second position, and designation as a point on the movement path of the arm; means for determining an interpolated posture by interpolating the first and second postures using a ratio of a distance between the determined target position and the central axis of the arm and a distance between the first and second positions; The arm at the target position is rotated around the central axis of the arm by an angle between a straight line passing through the first and second positions and a straight line connecting the target position and the center of the arm. Otf! An arm control system with f ridges can be obtained.

(Example) The present invention will be explained below using the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram in which an arm movement range check function is added to the embodiment of the invention shown in FIG. Third
The figure is a perspective view showing the coordinate system j used in the following explanation.

As shown in FIG. 3, in the following description, a direct firing coordinate thread XYZ with the main body center axis of the arm 6 as the Z axis will be considered as a reference coordinate system. Various methods can be considered to express the position and posture for specifying the motion path of the multi-joint arm 6, but here, as an example, we will use the position vector ′ with respect to the center of the hands 9 scattered at the tip of the arm 6. f: P,
The explanation will proceed assuming that a unit vector parallel to the direction of the hand 9 is kA, and a unit vector parallel to the opening/closing force direction of the hand 9 is S. However, all vectors P, A, and 8 are in the reference coordinate system
It shall be described by YZ. At this time, the position vector P corresponds to the position for specifying the motion path of the multi-joint arm 6, and the unit vectors ``person'' and ``S'' correspond to the posture.

In FIG. 1, first, in block 110,
First, position P1 and attitude AI at the point closest to the arm body central axis 2, 5it-teach, block 120
Second, the position P2 and the posture of the person 2 at the point farthest from the arm body center axis Z. Teach S2.

It is assumed that the positions P1 and P2 are selected so that the straight line connecting the positions P1 and P2t passes through the central axis z6. next,
In block 130, the distance between position P1 and the center axis of the arm body is determined as R1, in block 140, the distance between position P2 and the center axis of the arm body is determined as 111t''R2, and in block 150, the distance between position P2 and the center axis of the arm body 6 is determined as R1. and position P2t-
The rotation angle θ of the connected straight arm 6 around the main body center axis 2 turns 9
Find and memorize θ. The above operations are performed using arm 6.
It is sufficient to do this only once for each task, and there is no need to do it every time the task is executed. When you actually do the work @
First, specify the target position 1tPt-block 10,
In block 20, the distance between the target position P and the center axis of the arm body is determined as R. First of all, as a posture, the target position P
and the distance li! from the main body center axis 2 of the arm 6! I! R and the distance between the first and second two points Pl and P2 to determine the first and second postures AI, A2, 81. Interpolated postures A' and S' obtained by interpolating S2 are obtained from the following equations.

A'=((R-1(1) Book A2+ (R2-R) Book AI
)/CR2-R1) S'=((R-R1*82+CR2-M)181)
/(R2-R1) Next, in block 50, the first and second two points PL.

A straight line passing through P2, the target position P, and the arm body center axis Z
Find the angle θ between the straight line t-a and block 60.7.
0, the interpolated posture A/, s/ is rotated by the angle around the central axis 2 of the arm body using the following formula.

A target posture with respect to the target position P is determined.

A-RUTZ(θ)*A' 8=R(JTZ(θ)*S' However, there is one person, and S is a three-miss vector.

The target position P and attitude A obtained as described above.

By moving the arm to the target position and target posture in the St-block 80, respectively.

It becomes possible to control the motion path of the multi-joint arm by specifying only the target position.

Fig. 2 is another example of the present invention, which is the operating principle # of the arm control method shown in Fig. 1 with an arm movement range check function added! FIG.

As shown in Figure 1, firstly, the position and orientation at the point closest to the arm body central axis are taught and stored, and secondly, the position and orientation at the point farthest from the arm body central axis are taught and stored. This is similar to the method shown. In addition, when actually performing the work, the target position P is first specified in block 10, and the distance between the target position P and the center axis of the arm body is determined in block 20 as =<R. It is similar to In Fig. 2, the distance between the target position P and the center axis of the arm body is set at block 20.
After determining the distance, the distance R2 is compared with the distance R2 in block 25, and if R1≦R≦R2, the target position and target posture are determined in blocks 30 to 80 in the same manner as in Figure 1, and the arm is moved. Do the following. If the distance R does not satisfy the above range, it is determined that the target position itP is outside the movement range of the arm 6, and the arm 6 is not moved. According to the above operation, even when moving over a wide range, it is possible to automatically select the posture so as to effectively utilize the movement range of the arm 6, and it is also possible to automatically select the posture so as to effectively utilize the movement range of the arm 6. Movement outside the range is not performed, and inconvenient operations due to movement outside the specified range can be avoided.

The embodiment of the arm control method according to the present invention has been described above using the orthogonal coordinate system. However, when specifying the position and orientation using a polar coordinate system or a cylindrical coordinate system, and when specifying the position and orientation using Euler angles as the orientation, It is clear that the posture can be obtained in exactly the same way, and this modification can be easily deduced by analogy to those skilled in the art, so a more detailed explanation will be omitted.

An example of an optimal arm ilJ control device for implementing the arm control method according to the present invention will be described below with reference to the drawings.

FIG. 4 is a block diagram showing an example of an arm control device implementing the present invention. In the embodiment shown in FIG. 4, the arm 6 is moved by giving instructions to the arithmetic and control device 3 using the teaching device 4 in advance, and the position PI and posture of the arm 6 at the point closest to the main body center axis 2 are first determined. A
I, 81 is stored in the storage means 1i, and the arm 6 is stored as the second
The position P2 and attitude A2, 82 at the farthest point from the main body center axis 2) are stored in the storage means 2. When actually working, the teaching device 4. Or a visual device such as a camera7. Or the angle of the upper control device 8 etc.
Input only P to the arithmetic and control unit 0113, and
The arithmetic and control device 3 executes the operation explained using the igZ diagram to obtain the target posture A, 8 with respect to the target position, and causes the arm drive device 5 to determine the target position P and the spider group ÷÷≠ target. Give posture A, 8, and move arm 6. Storage means 1, 2t - writable/readable.

'If the trowel is configured so that the contents are retained even when the IIL source is turned off, it is sufficient to perform the teaching operation only once on the arm 6, and there is no need to perform it every time the work is performed. . In addition, the storage means 1.2 is configured with read-only data, and the position/orientation Pi, Al, 81
, P2. By incorporating A2.82,
As the teaching device 4, an inexpensive device capable of specifying only the position can be used.

Furthermore, although the storage means 1 and 2 are separated from the arithmetic and control unit 3 in FIG. 4, they may actually be placed within the arithmetic and control unit It3. Also, a teaching device 4 or a visual device 7 such as a camera. Alternatively, it is clear that the upper control device 8 etc. can be selected and used as necessary, and these modifications may be made without departing from the spirit of the present invention, and the above description does not exceed the scope of the present invention. It is not limited.

(Effects of the Invention) According to the present invention, in an arm control method for controlling a motion path of a multi-joint arm that requires specifying a target position and a target posture, when specifying a motion path.

It is only necessary to specify the target position, there is no need to specify the posture according to the position, and even when moving over a wide range, the posture is automatically selected so as to effectively utilize the arm movement range. This provides an arm control system that takes this into account.

In addition, it is possible to check the arm movement range by a simple calculation, and if this check is performed, the movement outside the range specified by the tightening instruction will not be performed, and it will be possible to check the arm movement range by a simple calculation. This has the great advantage of being able to inexpensively avoid inconvenient movements caused by movement. Furthermore, when specifying the range, it is sufficient to teach the position and orientation at two points close to the central axis of the arm body only once. There will be no increase in such effort.

As described above in detail, according to the present invention, it is possible to obtain an arm control system that eliminates the drawbacks of the conventional art.

[Brief explanation of drawings]

Figure 1 is a block diagram of an embodiment of the present invention, Figure 1@2 is a block diagram of Figure 1 with an arm movement range check function added, and Figure 3 is a coordinate system used to explain the operating principle. The perspective view shown in FIG. 4 is a block diagram showing an example of an arm control device implementing the present invention. In the figure, 1 and 2 are storage means, 3 is an arithmetic and control unit, and 4
5 is a teaching device, 5 is an arm drive device, 6 is an arm, 7 is a visual device, and 8 is a higher-level control device. Agent Patent Attorney Roku Uchihara ・′ 1゛、・・ $ 1 Figure

Claims (1)

[Claims] A first position that is the position of the arm closest to the central axis of the arm, a first posture that is the posture of the arm in this first position, and a position of the arm that is farthest from the central axis of the arm. means for storing a second position and a second posture that is a posture of the arm at the second position; and a target position designated as a point on a movement path of the arm and a central axis of the arm; means for determining an interpolated posture by interpolating the first and second postures using a ratio of the distance between the first and second positions; and means for determining the posture of the arm at the target position by rotating the arm around the central axis by an angle between a straight line passing through the target position and a straight line connecting the target position and the central axis of the arm. Arm control method.